Functional Stuff

Either.js

var Left = function(x) {
  this.__value = x;
};

Left.of = function(x) {
  return new Left(x);
};

Left.prototype.map = function(f) {
  return this;
};

var Right = function(x) {
  this.__value = x;
};

Right.of = function(x) {
  return new Right(x);
};

Right.prototype.map = function(f) {
  return Right.of(f(this.__value));
}

Functor.js

const Container = function(x) { this.__value = x; }

Container.of = function(x) {
  return new Container(x);
}

Container.prototype.map = function(f) {
  return Container.of(
    f(this.__value)
  );
}

// aplicative functor
Container.prototype.ap = function(other_container) {
  return other_container.map(this.__value);
}

export default Container;

IO.js

import compose from 'compose';
import prop from 'prop';

var IO = function(f) {
  this.execute = f;
};

IO.of = function(x) {
  return new IO(function() {
    return x;
  });
};

IO.prototype.map = function(f) {
  return new IO(compose(f, this.execute));
};

// usage eg:
// var winIO = new IO(()=>window);
// winIO.map(prop('location')).execute();

Maybe.js

var Maybe = function(x) {
  this.__value = x;
};

Maybe.of = function(x) {
  return new Maybe(x);
};

Maybe.prototype.isNothing = function() {
  return (this.__value === null || this.__value === undefined);
};

Maybe.prototype.map = function(f) {
  return this.isNothing() ? Maybe.of(null) : Maybe.of(f(this.__value));
};